Event ACRs Generated for Receipt of SIP Messages
An Event ACR is issued when the following SIP messages are received:
- 200 OK message for a SIP Register from the IMS core.
- SIP Final/Redirection Response 3xx
- SIP Final Response (4xx, 5xx or 6xx) — this indicates an unsuccessful session-unrelated procedure.
- SIP Final Response (4xx, 5xx or 6xx) — this indicates an unsuccessful SIP session set-up.
This example call flow shows an Event ACR that is created due to the reception of a 3xx SIP message. In this example the call fails after being redirected.

Event ACR Created Upon Reception of a 3xx Message Followed by Call Failure After Redirect
This example call flow shows an Event ACR that is created due to the reception of a 3xx SIP message. Then it shows a Start ACR upon reception of a 200OK. In this example the call succeeds after being redirected. The generate-start is OK.

Event ACR Created Upon Reception of a 3xx Message Followed by Call Success After Redirect
This example call flow shows a Start ACR being sent when an Invite is received and an Interim ACR that is created due to the reception of a 3xx SIP message. In this example the call succeeds after being redirected. The generate-start is Invite.
